This invention relates generally to fluid filtration, in particular to collection of a filtrate from a bulk fluid being sampled, and especially to sampling of a body fluid for biomedical analysis or to fermentate sampling.
U.S. Pat. Nos. 5,015,388 to Pusineri et al, 4,753,733 to Ramstack, 4,631,130 to Watanabe, 4,212,742 to Solomon et al, and 3,705,100 to Blatt et al illustrate prior art, filtration techniques. In apparatus of the Pusineri et al, Solomon et al, and Blatt et al patents, a bulk fluid is passed over a fluid side surface of a filtration medium; fluid which does not pass through the filtration medium is collected from the bulk fluid or upstream side; cross-flow filtration occurs; and filtrate is collected from the filtrate or downstream side of the filtration medium. The Ramstack process is directed to clearing membrane fouling.
A problem in filtration sampling can be backflow-caused contact between a filtrate and the filtration medium, with there being a potential for contamination of a bulk fluid being sampled, by any contaminants on the filtrate side of the filtration medium. Any contamination of a bulk fluid could have serious negative consequences. A further problem is filtration medium fouling. Also, in certain circumstances such as on-line biomedical sampling, air entrapment on the bulk fluid side of a filtration medium should be particularly avoided.
Accordingly, there is a need for an improved filtration apparatus, and in particular for an improved filtration apparatus useful for the collection of a filtrate from a bulk fluid being sampled. Beneficially, bulk fluid contamination would be prevented. Moreover, filtrate collection and thus bulk fluid sampling, upon demand, would be advantageously provided for. Furthermore, filtration medium fouling would be reduced. Such apparatus would be especially beneficial for certain on-line biomedical sampling if air entrapment on the bulk fluid side of a filtration medium could be avoided.